Hemiparesis of the lower limb is one of the most common impairments resulting from stroke. Approximately 80% of the over 780,000 strokes that occur annually in the United States result acutely in loss of ability to walk household distances independently. By 6 months after stroke, approximately 40% of all stroke survivors are still either unable to walk or require personal assistance to walk even short distances. The impact of lower limb impairment on disability and health is great;therefore, our long-term objective is to develop lower limb rehabilitation therapies that are effective at reducing impairment and improving ambulation, that are applicable across a wide range of impairment severity, and that are readily implemented in the present healthcare environment. A major contributor to impaired ambulation is the inability to dorsiflex the ankle during the swing phase of gait, which results in inefficient and unsafe ambulation or non-ambulation. This proposal investigates a new intervention that aims to reduce lower limb motor impairment and improve gait in stroke survivors with chronic lower extremity hemiplegia by improving voluntary ankle dorsiflexion. Contralaterally controlled neuromuscular electrical stimulation (CCNMES) incorporates several rehabilitation techniques shown to improve motor recovery. CCNMES activates the paretic ankle dorsiflexors through surface electrodes over the peroneal nerve and tibialis anterior. The stimulation intensity is directly proportional to the degree of volitional dorsiflexion of the unimpaired contralateral ankle, as detected by an instrumented sock. Thus, volitional dorsiflexion of the unaffected ankle produces stimulated dorsiflexion of the affected ankle, thereby enabling the patient to control their ankle movement. The system is not used for walking but for motor control therapy. The primary objective of the study is to collect pilot data estimating the effect of CCNMES therapy on lower extremity impairment and ambulation. Twenty-six chronic stroke survivors (>6 months post-CVA) with significant ankle dorsiflexor paresis will be randomized to CCNMES or cyclic NMES for six weeks and will be followed for 3 months. The six-week treatment consists of subject-administered stimulation-mediated ankle exercises at home 5 days a week plus therapist-supervised ankle motor control task practice in the laboratory twice a week. Outcome measures will include assessments of lower extremity impairment and ambulation. This study is the first randomized controlled trial of CCNMES for ankle dorsiflexor paresis. Ultimately, the information learned in this study will serve to accelerate the development of treatments for reducing post- stroke disability. PUBLIC HEALTH RELEVANCE: There is a need for more effective rehabilitation interventions for individuals who have become disabled by stroke. This study is an important step toward the development of a new treatment that may be found to be more effective in facilitating lasting motor recovery, more widely applicable to a broader range of stroke survivors, and more readily implemented than existing stroke rehabilitation techniques. As more effective stroke rehabilitation therapies are developed, the prevalence of post-stroke disability may be decreased.